Physical computing, in the broadest sense, means building interactive physical systems by the use of software and hardware that can sense and respond to the analog world. While this definition is broad enough to encompass things such as smart automotive traffic control systems or factory automation processes, it is not commonly used to describe them. In the broad sense, physical computing is a creative framework for understanding human beings' relationship to the digital world. In practical use, the term most often describes handmade art, design or DIY hobby projects that use sensors and microcontrollers to translate analog input to a software system, and/or control electro-mechanical devices such as motors, servos, lighting or other hardware.

Physical computing practices also exist in the product and interaction design sphere, where hand-built embedded systems are sometimes used to rapidly prototype new digital product concepts in a cost-efficient way. Firms such as IDEO and Teague are known to approach product design in this way.

Commercial implementations range from consumer devices such as the Sony Eyetoy or games such as Dance Dance Revolution to more esoteric and pragmatic uses such as machine vision used in the automation of quality inspection along a factory assembly line. Exergaming can be considered a form of physical computing. Other implementations of physical computing include voice recognition, which senses and interprets sound waves via microphones or other soundwave sensing devices, and computer vision, which applies algorithms to a rich stream of video data typically sensed by some form of camera. Haptic interfaces are also an example of physical computing, though in this case the computer is generating the physical stimulus as opposed to sensing it. Both motion capture and gesture recognition are fields that rely on computer vision to work their magic.

Physical computing can also describe the fabrication and use of custom sensors or collectors for scientific experiments, though the term is rarely used to describe them as such. An example of physical computing modeling is the Illustris project, which attempts to precisely simulate the evolution of the universe from the Big Bang to the present day, 13.8 billion years later.[1][2]